IEEE C802.16m-08/xxx
Project / IEEE 802.16 Broadband Wireless Access Working Group <Title / Coexistence Supports with E-UTRA TDD System
Date Submitted / 2008-09-05
Source(s) / Dongcheol Kim,
Sungho Moon,
Jin Sam Kwak
LG Electronics / Voice : +82-31-450-1852
E-mail:{dongcheol.kim; msungho; samji}@lge.com
Re: / PHY:Text; In response to the TGm Call for Contributions and Comments 802.16m-08/033 for Session 57
Abstract / This contribution proposes SDD text for the 802.16m based on IEEE 802.16m-08/003r4.
Purpose / To be discussed and adopted by TGm for use in the 802.16m SDD.
Notice / This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein.
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Coexistence Supports withE-UTRA TDD System
DongCheol Kim, Sungho Moon, and Jin Sam Kwak
LG Electronics
1.Introduction
The IEEE 802.16m system shall support co-deployment scenarios with E-UTRA TDD in the same or adjacent frequency band as mentioned in the IEEE 802.16m System Requirement Document (SRD) [1]. Therefore, the inter-system DL and UL alignment should be considered to prevent severe interference at the cell edge. However, E-UTRA TDD has configurations with a switch-point periodicity of 10 ms, which can cause large number of symbols or sub-frames puncturing for IEEE 802.16m system to avoid the interference from DL/UL mis-alignment. In this contribution, we consider coexistence scenarios between the IEEE802.16m TDD frames and E-UTRA TDD frames, and suggest asymmetric configuration and UL-alignment scheme for IEEE 802.16m to reduce the number of punctured symbols in all possible DL and UL configurations of E-UTRA TDD system.As a text proposal for the 802.16m System Description Document (SDD), we suggesttext and illustrationsondocument C802.16m-08/003r4, “Draft IEEE 802.16m System Description Document” [2].
2.Coexistence Methods
In the current SDD [2], there are two kinds of coexistence methods categorized by aligned points between two TDD systems. Fig. 1 shows the illustration in the current SDD for coexisting with LTE TDD(E-UTRA TDD) [3]. The first scheme can be called DL-aligned scheme in which the IEEE 802.16m TDD frame is aligned to the start point of consecutive DL sub-frames in LTE. In the second scheme, the IEEE 802.16m UL frame is aligned to the start of UpPTS or GP in LTE (or the start of consecutive UL region = UpPTS). If we assume that the reference time of IEEE 802.16m frame is the start point of consecutive DL sub-frames, the DL-aligned or UL-aligned offset can be defined as a delay of the IEEE 802.16m reference time from the LTE reference time.In both schemes, some DL and UL symbols can be punctured due to mis-alignment between DL and UL regions because sub-frame sizes and DL/UL configuration periods are different between the IEEE 802.16m and LTE TDDsystems. The punctured symbols should be minimized to maintain spectral efficiency in IEEE 802.16m. Thus, the DL and UL-aligned offset can be additionally shifted within RTG and/or TTG in the IEEE 802.16m system.
2.1Coexistence with10 ms Periodicity Frame Configurations
The LTE specification defines a 10 ms radio frame as two half-frames with a length of 5 ms, and each half-frame includes 5 sub-frames with a length of 1 ms. Within a frame, there are one or two special sub-frames consisting of DwPTS, GP and UpPTS. In the view point of IEEE 802.16m TDD frame, the UL/DL configuration of LTE TDD can be categorized into two cases by switch-point periodicity. Table 1 shows the downlink-uplink allocations in LTE TDD where “S” consists of DwPTS, GP, and UpPTS [3].
Fig. 1 Alignment examples of IEEE 802.16m and LTE TDD frames in SDD
Table 1. Downlink-Uplink Allocations in LTE TDD
Configuration / Switch-point periodicity / Sub-frame number1st half-frame / 2nd half-frame
0 / 1 / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 9
0 / 5 ms / D / S / U / U / U / D / S / U / U / U
1 / 5 ms / D / S / U / U / D / D / S / U / U / D
2 / 5 ms / D / S / U / D / D / D / S / U / D / D
3 / 10 ms / D / S / U / U / U / D / D / D / D / D
4 / 10 ms / D / S / U / U / D / D / D / D / D / D
5 / 10 ms / D / S / U / D / D / D / D / D / D / D
6 / 5ms / D / S / U / U / U / D / S / U / U / D
The configurations 3, 4, 5, and 6, which have 5ms/10 ms switch-point periodicity, have two different 5 ms frames within a 10 ms LTE TDD frame, and thus, it’s obvious that there will be a large number of punctured symbols when IEEE 802.16m TDD frame have the same DL to UL ratio for every frame.
Fig. 2 shows a coexistence scenario where the IEEE 802.16m frame is delayed by DL-aligned offsetwith the frame configuration 4 in LTE. The whole sub-frames mis-aligned with LTE should be punctured, and it can cause 25% loss in the spectral efficiency of IEEE 802.16m. In order to prevent this kind of sub-frame puncturing with LTE configuration 3, 4, and 5,asymmetric frame configurations, in which each frame can have a different DL to UL ratio from others, should be considered for IEEE 802.16m TDD.
In the configurations 3, 4, and 5, since the 1st half-frames are the same as the frames in the configurations 0, 1, and 2, respectively, and the 2nd half-frames consist of all DL sub-frames, asymmetric frame configuration with the same offset values derived from the configurations 0, 1, and 2 can be used as well. Because the all-DL part cause no symbol puncturing in the asymmetric frame configuration, the numbers of punctured symbols are the exactly same as those in the configuration 0, 1, and 2. The optimized DL to UL ratio can be defined as the combinations of all-DL ratio, i.e., 8:0 and the DL to UL ratio used in configuration 0, 1, and 2. Therefore, possible DL to UL ratio of IEEE 802.16 to coexist with 10 ms switch-point periodicity LTE frames can be 10:6, 11:5, 12:4, 13:3, 14:2, and 15:1.
Fig. 2Asymmetric frame configuration for 10 ms switch-point periodicity in LTE
In the configuration 6, the 2nd half-frame does not consist of all-DL sub-frames, and thus, an asymmetric frame configurationcan minimize punctured symbols. Since three DL sub-frames are spread across one LTE frame, it is not possible to use a DL-aligned asymmetric configuration.One sub-frame of LTE is 1 ms which is covered by 8 symbols in IEEE 802.16. Therefore, both DL-aligned asymmetric and DL-aligned symmetric configurations must yield more than 8 punctured symbols every 10 ms. However, we can find an available UL-aligned asymmetric configuration in which the number of punctured symbols is smaller than 8 for all DwPTS, GP, and UpPTS cases. Therefore, the UL-alignment is necessary to minimize punctured symbols in case of configuration 6 in LTE.
Fig. 3 shows an UL-aligned asymmetric frame configuration with frame configuration 6. The UL-aligned offsetis the delay time of IEEE 802.16m 10 ms frame, which is newly defined as shown in Fig. 3, in the viewpoint of LTE TDD frame. The reference time of IEEE 802.16m is the start point of the DL region which has more consecutive DL sub-frames than the other.
Fig. 3. Asymmetric frame configuration for LTE configuration 6 (the 8th case of normal CP)
The UL-aligned asymmetric frame configuration can reduce the number of punctured symbols with LTE configuration 6. However, there exist multiple switching points between DL and UL in the odd frame, and thus, this configuration can be only used for legacy-support disabled mode. If theIEEE 802.16m operates as legacy-support mode, DL-aligned or UL-aligned symmetric frame configurations should be applied to coexist with LTE configuration 6.The detailed frame alignment methods, offset, DL to UL ratios to minimize punctured symbols are summarized at Table A.1 in the Appendix.
3.Conclusion
We can summarize main results in this contribution as follows:
To minimize the number of punctured symbols, one of DL-aligned and UL-aligned scheme can be selectively used for each configuration.
To coexist with a frame configuration of 10 ms switch-point periodicity, asymmetric frame configurations should be considered for the IEEE802.16m TDD.
The UL-alignment is necessary to minimize punctured symbols in configuration 6 ofE-UTRA TDD.
4.References
[1]IEEE 802.16m-07/002r4, “IEEE 802.16m System Requirements”.
[2] IEEE 802.16m-08/003r4, “Draft IEEE 802.16m System Description Document”.
[3] 3GPP TS 36.211: "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation
Text Proposal for the 802.16m SDD
Add the following text at the end of section 11.4.5.1 in IEEE 802.16m-08/003r4.
======Start of Proposed Text ======
As coexisting with E-UTRA TDD operating in a configuration of 10ms switch-point periodicity, the IEEE 802.16m shall support asymmetric DL/UL configurations within a 10 ms period to minimize the number of punctured symbols or subframes.
======End of Proposed Text ======
Appendix
Table A.1.Alignment scheme (DL or UL-aligned), offset(), and DL/UL ratio of IEEE 802.16m with configurations of 10 ms switch-point periodicity
*PS : punctured symbol
Configuration / 3 / 4 / 5 / 6LTE TDD DL/UL Ratio / 6:3 / 7:2 / 8:1 / 3:5
NormalCP / Align, offset, and
PS / Asymmetric 10ms DL:UL / Align, offset, and
PS / Asymmetric 10ms DL:UL / Align, offset, and
PS / Asymmetric 10ms DL:UL / Align / offset / Asymmetric
10ms DL:UL / PS
0 / The same as configuration 0 / 10:6
or
11:5 / The same as configuration 1 / 12:4 / The same as configuration 2 / 14:2 / UL / 9458.07 / 4:5:3:4
(DL:UL:DL:UL) / 5
1 / 11:5 / 13:3 / 14:2 / UL / 9458.07 / 4:5:3:4
(DL:UL:DL:UL) / 5
2 / 11:5 / 13:3 / 14:2 / UL / 9458.07 / 4:5:3:4
(DL:UL:DL:UL) / 5
3 / 11:5 / 13:3 / 14:2 / UL / 9458.07 / 4:5:3:4
(DL:UL:DL:UL) / 5
4 / 11:5 / 13:3 / 14:2 / UL / 9386.72 / 4:5:3:4
(DL:UL:DL:UL) / 4
5 / 10:6
or
11:5 / 12:4 / 14:2 / UL / 9386.72 / 4:5:3:4
(DL:UL:DL:UL) / 4
6 / 11:5 / 13:3
or
12:4 / 14:2 / UL / 9386.72 / 4:5:3:4
(DL:UL:DL:UL) / 4
7 / 11:5 / 13:3
or
12:4 / 14:2 / UL / 9386.72 / 4:5:3:4
(DL:UL:DL:UL) / 4
8 / 11:5 / 13:3 / 14:2 / UL / 9386.72 / 4:5:3:4
(DL:UL:DL:UL) / 4
Extended CP
0 / The same as configuration 0 / 11:5 / The same as configuration 1 / 12:4 / The same as configuration 2 / 14:2 / UL / 9396.35 / 3:6:2:5
(DL:UL:DL:UL) / 4
1 / 11:5 / 13:3 / 15:1
or
14:2 / UL / 9446.1 / 4:5:3:4
(DL:UL:DL:UL) / 5
2 / 11:5 / 13:3 / 15:1
or
14:2 / UL / 9446.1 / 4:5:3:4
(DL:UL:DL:UL) / 5
3 / 11:5 / 13:3 / 15:1 / UL / 9446.1 / 4:5:3:4
(DL:UL:DL:UL) / 5
4 / 11:5 / 12:4 / 15:1 / UL / 9396.35 / 3:6:2:5
(DL:UL:DL:UL) / 4
5 / 11:5 / 13:3
or
12:4 / 14:2 / UL / 9196.097 / 4:6:2:4
(DL:UL:DL:UL) / 6
6 / 11:5 / 13:3 / 14:2 / UL / 9279.43 / 4:5:3:4
(DL:UL:DL:UL) / 8
1